Lie face-down on the incline bench with your butt on the end of the bench, hold one dumbbell between your two feet in the air, keep your legs straight and parallel to the bench, and your hands had better grab the end of bench to keep your torso stationary on the bench. That is your starting position
Keep your torso stationary on the bench, contract your legs to raise your legs until it maintain almost 90 degree between your legs and the bench, hold the position for two seconds to squeeze your legs
Then, slowly lower your dumbbells back to the starting position
Breathe out when raising and in when lowering
Tips:
Keep your torso straight during the whole process
